RFR: 8189171: Move GC argument processing into GC specific classes

[David Holmes]

Hi Roman,

Not a review as GC folk need to do that.

On 13/10/2017 5:59 AM, Roman Kennke wrote:
> I'm posting it to both hotspot-runtime-dev and hotspot-gc-dev because it 
> touches both areas (i.e. the GC interface).
> 
> Currently, all GC related argument processing is done in arguments.cpp, 
> littering it with #ifdef INCLUDE_ALL_GCS and all sorts of GC specific 
> methods etc.

 From a runtime perspective I like all the GC specific ifdefs and 
settings moved out-of-line of the main argument processing.

 From a refactoring perspective I noticed that set_object_alignment() no 
longer calls set_cms_values(). I presume setting it elsewhere is okay?

Thanks,
David

> In order to have a cleaner GC interface, I propose to move all that code 
> into GC specific classes under their GC specific directories.
> 
> Since at this point in time we haven't created the XXXHeap subclasses 
> yet (and cannot, before having set up all the flags and arguments), I 
> propose to create a GC interface of which we create an instance as soon 
> as we have selected a GC, and then do argument processing there.
> 
> This 'GC' interface is, at this point, meant as a sort of GC factory 
> interface. With this patch, it will only do argument processing. Later I 
> plan to add heap creation to it (which is currently done in 
> universe.cpp, with INCLUDE_ALL_GCS stuff and all the if (UseBlahGC) .. 
> else if .. else branch chains. My current prototype in the jdk10 sandbox 
> also provides servicabilty support classes and some more stuff, but we 
> should decide later where to put this.
> 
> I broke out some code paths into gc_factory.cpp (i.e. not in gc.cpp). 
> Those are all the code paths that select GC, create the right instances, 
> etc, in other words, the code paths that need to know about all GCs. 
> Ideally, this should be the only file that needs to know about all the 
> GCs. (Suggestions for improvement are welcome of course.)
> 
> I tested this by running hotspot_gc jtreg tests, with normal fastdebug 
> and no-precompiled configurations. Everything passes fine.
> 
> http://cr.openjdk.java.net/~rkennke/8189171/webrev.00/ 
> <http://cr.openjdk.java.net/%7Erkennke/8189171/webrev.00/>
> 
> Opinions?
> 
> Roman
>